The objectives of this project fall into categories as follows: 1. To investigate the genetic and population aspects of the Gm and Inv allotypes in humans to provide a better insight into the evolution of man and to learn more about the genetics of antigens. The latter includes searching for new antigens. 2. To investigate the distribution of the Gm and Inv allotypes among baboon troops of known origin to gain insight into the evolution of the allotypes and into the population dynamics of gene distribution. 3. To determine the relation of the antigens to the structure of the IgG molecules to gain a better understanding of genetic control of polypeptides and of the nature of antigens. 4. To search for selection factor (s) responsible for the distribution of the allotypes in man.